Optical devices often include different optical components for processing of light signals. At one or more times during the fabrication of these components, a planarization may be performed using methods such as chemical-mechanical polishing. Planarization smoothes out the upper surface of the device so that the tops of the different features on the wafer are flush with one another. However, these planarization techniques often consume the underlying materials at rates that are not uniform across the device. As a result, there is a need for an improved process of planarizaing optical devices.